Temperature dependence of the coercive field in MnBi single crystals

The temperature dependence of ihe coercive field was measured on low-temperature phase MnBi single crystals between room-temperature and the Curie point. The wall-nucleation field Hnincreases more than one order of magnitude over this temperature range and values for Hnas high at 6-10 kOe were observed. This dependence of Hnon temperature is reversible with thermal cycling and the transition from a wall-motion-type hysteresis to a nucleation-type hysteresis is attributed to a temperature-dependent concentration of defects in the material. The results are compared with recent work on polycrystalline MnBi thin films and single crystal platelets.